As defined in Flexography, Principles and Practices, third edition, flexography "is a method of direct rotary printing using resilient raised image printing plates, affixable to plate cylinders of various repeat lengths, inked by a roll or doctor blade wiped metering roll, carrying fluid or paste type inks to virtually any substrate", although the term has even more broadly been used. The only widely accepted method of duplicating the flexographic printing process on a small scale is through the use of flexographic hand proofers. Although there are several commercial models available, all provide the same basic mode of operation, viz., applying ink to the substrate by manually rolling the hand proofer across the substrate.
Such prior art hand proofers are characterized in operation by two major variables. First, the speed with which the operator rolls the hand proofer varies from operator to operator and even with the same operator. Second, the pressure with which the operator presses the hand proofer onto the substrate varies in the same way. Because of these variables, it is virtually impossible to obtain repeatable proofs, i.e., proofs which are substantial duplicates of each other, even using the same hand proofer and the same ink, particularly if different operators are involved.
Patents relating to printing or embossing devices which are of possible interest with respect to the present invention include: U.S. Pat. Nos. 1,979,927 (Andersen); 2,991,713 (McFarland); 3,361,060 (Hoexter et al); 3,578,766 (Diolot); 3,894,488 (Gazzola); 3,987,726 (Corse); and 4,627,342 (Yui). Briefly considering these references, the Hoexter et al patent discusses flexographic printing and discloses a machine for mounting and proofing rubber printing plates wherein the impression cylinder and the plate cylinder are "locked" into engagement with each other. The Andersen and McFarland patents disclose hand printers, with the latter patent being concerned with a device for inking the roller of a portable proof press. The Corse patent discloses a rotary offset press wherein a spring arrangement creates pressure between blanket and engraved cylinders. The Diolot and Gazzola patents disclose an embossing machine and an intaglio press, respectively, wherein hydraulics are used to control the pressure exerted. The Yui patent discloses a printer including a clutch-brake unit.